With the rapid progress of the display technique, as a core of a display device, the technique of semi-conductor elements also makes rapid progress. For the existing display device, an organic light emitting diode (OLED), as a current-type light emitting device, is increasingly applied in high performance display area due to its characteristics of self-illumination, fast response, broad view and being able be to made on a flexible substrate.
OLED can be divided into a passive matrix driving OLED (PMPLED) and an active matrix driving OLED (AMOLED) according to driving modes. AMOLED display is expected to become a next generation of new flat panel display to take the place of a liquid crystal display (LCD) because it has advantages of low manufacturing cost, fast response speed, power saving, being applicable to direct current driving of a portable device, and wide range of operation temperature, etc.
In the existing AMOLED display panel, each OLED comprises a plurality of thin film transistor (TFT) switch circuits. However, due to characteristics of polysilicon and manufacturing process, it is caused that fluctuations often occur to electrical parameters such as a threshold voltage Vth, a mobility, etc. when the TFT switch circuit is manufactured on a large-area glass substrate, such that current flowing through the OLED device in the AMOLED display panel would not only change with turn-on voltage stress caused by long turn-on of TFT but also would become different as the threshold voltage Vth of TFT drifts. In this way, brightness uniformity and brightness constancy of the display would be influenced to reduce quality of pictures of the display.